Types of Ion Chromatography

This book only discusses separation methods that can be summarized under the general term ion chromatography. Modern ion chromatography as an element of liquid chromatography is based on three different separation mechanisms, which also provide the basis for the nomenclature in use. 

The separation mechanism in ion-exclusion chromatography is governed by Donnan exclusion, steric exclusion, sorption processes and, depending on the type of separator column, by hydrogen bonding. A high-capacity, totally sulfonated 

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Two types of ion chromatography are currently in use suppressor-based and single-column. They differ in the method used to prevent the conductivity of the eluting electrolyte from interfering with the measurement of analyte conductivities. 

Modem ion chromatography was first reported in 1975 in a landmark paper by Small, Stevens, and Bauman. At present, there are two main types of ion chromatography suppressed ion chromatography and non-suppressed ion chromatography. Ion exchange remains the primary separation mode used in ion chromatography today, although the apparatus used for the separation of the... 

In contrast to vapour phase chromatography, the mobile phase in liquid chromatography is a liquid. In general, there are four main types of liquid chromatography adsorption, partition, ion-chromatography, and gel filtration. 

Ion-exchange chromatography involves an electrostatic process which depends on the relative affinities of various types of ions for an immobilised assembly of ions of opposite charge. The stationary phase is an aqueous buffer with a fixed pH or an aqueous mixture of buffers in which the pH is continuously increased or decreased as the separation may require. This form of liquid chromatography can also be performed at high inlet pressures of liquid with increased column performances. 

New types of ion exchange resins have also been developed to meet the specific needs of high-performance liquid chromatography (HPLC) (Chapter 8). These include pellicular resins and microparticle packings (e.g. the Aminex-type resins produced by Bio-Rad). A review of the care, use and application of the various ion exchange packings available for HPLC is given in Ref. 19. 

A flow scheme for the basic form of ion chromatography is shown in Fig. 7.3, which illustrates the requirements for simple anion analysis. The instrumentation used in IC does not differ significantly from that used in HPLC and the reader is referred to Chapter 8 for details of the types of pump and sample injection system employed. A brief account is given here, however, of the nature of the separator and suppressor columns and of the detectors used in ion chromatography. 

Experimental values correlated well with the predicted ones proving that the model is a valuable addition to the theory of ion chromatography [98], Many synthetic dyes are sulphonated derivatives of complicate organic molecules. Because of their strong adsorption capacity their separation under traditional RP-HPLC conditions is sometimes difficult. Anion chromatography offers an advantageous alternative for the analysis of this type of synthetic dyes. 

A. Bartha, G. Vigh, H. Billiet, and L. de Galan, Effect of the type of ion-pairing reagent in reversed-phase ion-pair chromatography , Chromatographia, 1985,10, 587. 

The amount of polymer adsorbed on each sample was measured by pressure filtration through a 0.1 m filter, followed by analysis of the filtrate for residual polymer by gel permeation chromatography with refractive index determination. Particle zeta potentials were measured by taking a small sample of the solids from the centrifuge and re-suspending them in the supernatant prior to analysis in a Malvern Instruments Zetasizer . The concentration of all other types of ions in the supernatant was analysed by ICP atomic emission spectroscopy. 

Particularly in the case of ion chromatography and high performance liquid chromatography throughout the text, various types of detectors are discussed which when connected to the outlet of the separation detect effluents as they leave the column. 

Although this technique of ion suppression is frequently used in ion exchange chromatography, depending on the nature of the separation, a specific type of ion suppression column or exchange membrane may be required that will be appropriate for the phase system that is chosen and the analyte ion involved. 

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